Enhanced oil recovery method using injection well including two passages

ABSTRACT

The method enables enhanced recovery of oil contained in an underground oil reservoir by using an injection well including two passages of a water passage and a gas passage. The enhanced oil recovery method includes steps of injecting an injection water from the water passage, injecting an injection gas from the gas passage and spraying the injection gas as a fine gas bubble flow through a micro-bubble generator which is installed at a lower end of the gas passage, and penetrating into the underground oil reservoir a gas-liquid mixture fluid containing micro-bubbles generated by mixing the injection water and the fine gas bubble flow in the injection well.

TECHNICAL FIELD

The present invention relates to an enhanced oil recovery method using an injection well including two passages.

Priority is claimed on Japanese Patent Application No. 2020-153491, filed Sep. 14, 2020, the content of which is incorporated herein by reference.

BACKGROUND ART

A measure against global warming is an important problem for countries around the world to tackle with all their might. The introduction of a global carbon dioxide capture and storage technology (hereinafter abbreviated as “CCS” in the present specification) and a carbon dioxide capture, utilization and storage technology (hereinafter abbreviated as “CCUS” in the present specification) is required as an urgent response, as one of the measures against global warming.

The CCS is highly expected as a technology capable of significantly reducing carbon dioxide (hereinafter abbreviated as CO₂ gas in the present specification). However, the worldwide dissemination has not progressed as expected. There are several reasons for this, such as technological uncertainty, concerns about the safety of reservoirs, and underdeveloped laws and regulations, but it may be difficult to predict business feasibility, especially due to increased costs. Therefore, the CCUS, which aims not only to store recovered CO₂ gas, but also to produce value-added products by directly or indirectly using CO₂ gas to compensate for the cost of recovery, is gaining attention.

Therefore, a technology to inject gas containing CO₂ gas into an underground oil reservoir using enhanced oil recovery (hereinafter abbreviated as “EOR” in the present specification), which is one of the CCUS technologies, is a technically reliable technology. The EOR can be stored CO₂ gas underground as a measure against global warming, and economic effect can be improved while increasing oil recovery rates. Therefore, the EOR has become an indispensable element in the spread of CCUS technology in each country.

As a method of storing a large amount of CO₂ gas underground, there is a method of injecting CO₂ gas into an underground aquifer.

Patent Document 1 is characterized in that the CO₂ gas stored in the CO₂ gas tank is boosted by a pumping device, and the CO₂ gas is micro-bubbled by injecting it from an injection well drilled vertically to the formation, and the CO₂ gas is stored underground by dispersing the microbubbles in the formation water. A storage device and a storage method are proposed.

Patent Document 2 is characterized in that CO₂ gas is injected underground by a pumping device from an injection well drilled horizontally in the formation, the CO₂ gas is made into microbubbles, and the microbubbles are dispersed in the formation water to store the CO₂ gas underground. A storage device and a storage method have been proposed.

Patent Document 3 is characterized in that the injected gas is micro-bubbled on the ground surface and mixed with the injection water to create a gas-liquid mixed fluid, which is injected into the oil layer or the gas layer from the injection well to fine gaps in the layer. An enhanced recovery method and an enhanced recovery system for oil or natural gas, which is characterized by enhanced recovery of oil or gas by microbubbles in injection water, have been proposed.

CITATION LIST Patent Documents [Patent Document 1]

Japanese Patent No. 5315346

[Patent Document 2]

Japanese Patent No. 5399436

[Patent Document 3]

Japanese Unexamined Patent Application, First Publication No. 2008-019644

SUMMARY OF INVENTION Technical Problem

In Patent Document 1 and Patent Document 2, a filter is provided at the tip or the lower side of the injection well for pumping a stored material containing CO₂ gas. In Patent Document 1 and Patent Document 2, when mixing the pumped fluid as a gas-liquid mixture fluid, fine suspended solids in the liquid can clog the filter. Patent Document 3 installs a micro-bubble generator in the upper portion of an oil well (inside a well near the ground surface at a depth of 5 m to 50 m). In Patent Document 3, in the process of transporting micro-bubbles to the underground reservoir layer that exists several thousand meters underground, the leakage of micro-bubble water from a joint in the tubing or casing is unavoidable, and the change in formation temperature and pressure induces changes in the properties of the micro-bubble water, such that there is a risk that the replacement of oil and gas with micro-bubble water will not proceed as initially assumed.

Therefore, the inventors have found that the injection gas and the injection water are separately injected into the injection well by using an injection well including two passages, and the injection gas is passed through a micro-bubble generator installed at the lower end of the gas passage to efficiently generate the micro-bubbles and to efficiently penetrate the micro-bubbles into the gaps of the underground oil reservoir.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for enhanced recovery of oil contained in an underground oil reservoir by using micro-bubbles.

Solution to Problem

In order to solve the above problem and achieve the above object, the present invention employs the following aspects.

(1) An enhanced oil recovery method according to an aspect of the present invention is an enhanced oil recovery method for enhanced recovery of oil contained in an underground oil reservoir by using an injection well including two passages of a water passage and a gas passage, the enhanced oil recovery method including a step of injecting injection water from the water passage, a step of injecting an injection gas from the gas passage and spraying the injection gas as a fine gas bubble flow through a micro-bubble generator which is installed at a lower end of the gas passage, and a step of penetrate into the underground oil reservoir a gas-liquid mixture fluid containing micro-bubbles generated by mixing the injection water and the fine gas bubble flow in the injection well.

(2) In the enhanced oil recovery method described in (1) above, the water passage may be a water injection pipe, and the gas passage may be a gas injection pipe.

(3) In the enhanced oil recovery method described in (1) above, the gas passage may be arranged inside the water passage, and the injection water may be injected between an inside of the water passage and an outside of the gas passage.

(4) In the enhanced oil recovery method described in (1) above, the water passage may be arranged inside the gas passage, and the injection gas may be injected between an inside of the gas passage and an outside of the water passage.

(5) In the enhanced oil recovery method described in any one of (1) to (4) above, the micro-bubble generator may be installed at a depth where the underground oil reservoir is located.

Advantageous Effects of Invention

According to the above aspect of the present invention, it is possible to provide a method for enhanced recovery of oil contained in an underground oil reservoir by using micro-bubbles.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view for explaining an enhanced oil recovery method according to the first embodiment of the present invention.

FIG. 2 is a schematic view for explaining an enhanced oil recovery method according to the second embodiment of the present invention.

FIG. 3 is a schematic view for explaining an enhanced oil recovery method according to the third embodiment of the present invention.

FIG. 4 is a schematic view showing an example of a micro-bubble generator.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments for performing the present invention will be specifically described with reference to the drawings. In the following description, components common to each embodiment may be designated by the same reference numerals and duplicate description thereof may be omitted.

First Embodiment

The enhanced oil recovery method according to the first embodiment will be described with reference to FIGS. 1 and 4 .

FIG. 1 is a schematic view for explaining an enhanced oil recovery method according to the present embodiment.

As shown in FIG. 1 , the recovery of oil contained in an underground oil reservoir 212 is enhanced by using an injection well 101 including two passages of a water passage 104 and a gas passage 105. The enhanced oil recovery method according to the present embodiment includes a step of injecting injection water 102 from the water passage (water injection pipe) 104, a step of injecting an injection gas 103 from the gas passage (gas injection pipe) 105 and spraying the injection gas 103 as a fine gas bubble flow through a micro-bubble generator 210 installed at a lower end of the gas passage 105, and a step of penetrate a gas-liquid mixture fluid containing micro-bubbles by mixing the injection water 102 and a fine gas bubble flow generated from the micro-bubble generator 210 in the injection well 101 into the underground oil reservoir 212.

As shown in FIG. 1 , parts other than the upper end of the injection well 101 are embedded in the ground surface 211. The lower end of the injection well 101 reaches the depth at which the underground oil reservoir 212 is located. The injection well 101 is including two passages of the water passage 104 and the gas passage 105.

The injection water 102 is injected from the water passage 104 on the ground surface 211 side. River water and sea water are used as the injection water 102, but the formation water and injection water produced from a production well may also be reused by mixing them with river water and sea water. However, in any of the cases, since water other than the formation water is injected, a chemical agent is added before the injection so as not to cause blockage of the fine gaps due to formation swelling by the injection water.

The injection gas 103 is injected from the gas passage 105 on the ground surface 211 side. The injection gas 103 is hydrocarbon gas, flare gas, nitrogen gas, CO₂ gas, exhaust gas, or a gas that is a mixture of these. When CO₂ gas or exhaust gas is used as the injection gas 103, CO₂ gas can be stored underground, which is effective in combating global warming.

In the present embodiment, the water passage 104 and the gas passage 105 are arranged in parallel in the injection well 101. That is, the injection gas 103 and the injection water 102 are separately injected into the injection well 101. In other words, in the present embodiment, there is a structure in which a pipe 202 a constitutes two passages with two pipes, i.e., the water passage (water injection pipe) 104 and the gas passage (gas injection pipe) 105.

The micro-bubble generator 210 whose central material is a filter, which is a porous member, is installed at the lower end of the gas passage 105. The micro-bubble generator 210 is installed at the depth at which the underground oil reservoir 212 is located. As shown in FIG. 4 , in the case of the present embodiment, a shape of the filter has a cylindrical shape. When installed on an outer pipe of a dual channel pipe in the embodiment described later, the shape of the filter is a hollow coaxial cylindricality.

As the filter, for example, a member obtained by mixing and sintering ceramic particles and a binder for binding the particles, or a stainless steel sintered filter can be used. When the filter pore size is small, micro-bubbles are likely to be generated, but the passage resistance of a fluid increases, the pumping device for increasing the flow rate of the injection gas 103 is increased in size. In addition, when the filter pore size is increased, the passage resistance of the fluid decreases, but the efficiency of micro-bubbling generator is degraded, and further, it is not preferable that the injection water passes through the micro-bubble generator 210, since there is a possibility that floating particle in the injection water may clog the filter. The micro-bubbles refer to bubbles with a diameter of less than 1 mm (including a supercritical state).

According to the present embodiment, the injection gas 103 and the injection water 102 are separately pumped into the well, the fine gas bubble flow is sprayed through the micro-bubble generator 210, and the gas-liquid mixture fluid containing the micro-bubbles generated by mixing the injection water 102 and the fine gas bubble flow is penetrated into the gaps of the underground oil reservoir 212, whereby oil, natural gas, and formation water can be discharged from the fine gaps of the underground oil reservoir 212. This makes it possible to enhance the recovery of oil and natural gas.

The micro-bubble generator 210 may be installed at the depth at which the underground oil reservoir 212 at the lower end of the injection well 101 is located. The depth at which the underground oil reservoir 212 is located is a position corresponding to the depth of the underground oil reservoir 212 distributed on an outer periphery of the lower end of the injection well 101. By installing the micro-bubble generator 210 at the depth at which the underground oil reservoir 212 is located, it is possible to suppress the disappearance of the generated micro-bubbles and penetrate the micro-bubbles into the underground oil reservoir 212.

A packer 203 prevents the injection water 102 discharged from the lower end of the water passage 104 and the injection gas 103 discharged from the lower end of the gas passage 105 from flowing back to the ground surface.

The water passage 104 may be a water injection pipe. The gas passage 105 may be a gas injection pipe.

As described above, according to the present embodiment, the injection gas 103 and the injection water 102 are separately injected into the injection well 101 by using the injection well 101 including two passages, and the micro-bubbles are efficiently generated by passing the micro-bubble generator 210, and the gas is sprayed as a fine gas bubble flow. The gas-liquid mixture fluid containing the micro-bubbles generated by mixing with the injection water 102 in the well efficiently penetrate the underground oil reservoir 212. As a result, due to the effect that the gas-liquid mixture fluid containing the micro-bubbles is penetrated to the fine gaps in the underground oil reservoir 212, the production rate of oil and natural gas from the production wells drilled at different points from the injection well 101 will increases. As a result, the recovery of the oil and natural gas contained in the underground oil reservoir 212 can be enhanced.

The injection water and the injection gas moved from the injection well 101 to the production well together with the oil, the natural gas, and the formation water discharged from the fine gap by the micro-bubbles in the underground oil reservoir 212 are produced from the production well. A production fluid is produced through the inside of a tubing pipe among the devices that reuse the separated natural gas and injection gas, and formation water and injection water into the injection well. A three-phase gas-liquid separator for separating the production fluid with different specific gravity on the ground surface separates natural gas and injection gas, oil, and formation water and injection water, and the natural gas and the injection gas are transferred to an injection gas tank and reused as injection gas. The separated formation water and injection water are also transferred to the injection water tank and reused as injection water.

(Note: a pipe used to produce oil and natural gas from the underground oil reservoir is called a tubing pipe, and the gas-liquid mixture fluid of oil, natural gas, injection gas, formation water, and injection water pass upward.)

Second Embodiment

Next, the enhanced oil recovery method according to the second embodiment will be described with reference to FIG. 2 , but the basic configuration is the same as that of the first embodiment. Therefore, the same reference numerals are given to the same components, the description thereof will be omitted, and only the differences will be described.

The second embodiment is different from the first embodiment in that a gas passage 205 is arranged inside a water passage 204, and the injection water 102 is injected between the inside of the water passage 204 and the outside of the gas passage 205.

FIG. 2 is a schematic view for explaining an enhanced oil recovery method according to the present embodiment.

As shown in FIG. 2 , in the enhanced oil recovery method according to the present embodiment, the gas passage (inner pipe) 205 is arranged inside the water passage (outer pipe) 204. That is, the injection well 201 according to the present embodiment has a structure of a pipe 202 b that constitutes two passages with the dual channel pipe of the water passage (outer pipe) 204 and the gas passage (inner pipe) 205. In the present embodiment, the injection water 102 is injected between the water passage 204 and the gas passage 205, the injection gas 103 is injected into the gas passage 205, and the micro-bubble generator 210 is installed at the lower end of the gas passage 205.

The same effect as that of the first embodiment can be obtained in the present embodiment. That is, the micro-bubbles are efficiently generated by passing through the micro-bubble generator 210 is installed at the lower end of the gas passage 205, and the gas is sprayed as a fine gas bubble flow. The gas-liquid mixture fluid containing the micro-bubbles generated by mixing with the injection water 102 in the well efficiently penetrates the underground oil reservoir 212. As a result, due to the effect that the gas-liquid mixture fluid containing the micro-bubbles is penetrate to the fine gaps in the underground oil reservoir 212, the production rate of oil and natural gas from the production wells drilled at different points from the injection well 201 will increases. As a result, the recovery of the oil contained in the underground oil reservoir 212 can be enhanced.

Further, when the structure has the dual channel pipe as in the present embodiment, since it can be handled as a single pipe, the effect of reducing a work over cost and a down hole tools cost is expected.

Third Embodiment

Next, the enhanced oil recovery method according to the third embodiment will be described with reference to FIG. 3 , but the basic configuration is the same as that of the first embodiment. Therefore, the same reference numerals are given to the same components, the description thereof will be omitted, and only the differences will be described.

The third embodiment is different from the first embodiment in that the water passage 304 is arranged inside the gas passage 305, and the injection gas 103 is injected between the inside of the gas passage 305 and the outside of the water passage 304.

FIG. 3 is a schematic view for explaining an enhanced oil recovery method according to the present embodiment.

As shown in FIG. 3 , in the enhanced oil recovery method according to the present embodiment, the water passage (inner pipe) 304 is arranged inside the gas passage 305 (outer pipe). That is, the injection well 301 according to the present embodiment has a structure of a pipe 202 c that constitutes two passages with the dual channel pipe of the gas passage (outer pipe) 305 and the water passage (inner pipe) 304. In the present embodiment, the injection water 102 is injected into the water passage 304, the injection gas 103 is injected between the inside of the gas passage 305 and the outside of the water passage 304, and the micro-bubble generator 210 is installed at the lower end of the gas passage 305.

The same effect as that of the first embodiment can be obtained in the present embodiment. That is, the micro-bubbles are efficiently generated by passing through the micro-bubble generator 210 is installed at the lower end of the gas passage 305, and the gas is sprayed as a fine gas bubble flow. The gas-liquid mixture fluid containing the micro-bubbles generated by mixing with the injection water 102 in the well efficiently penetrates the underground oil reservoir 212. As a result, due to the effect that the gas-liquid mixture fluid containing the micro-bubbles is penetrated to the fine gaps in the underground oil reservoir 212, the production rate of oil and natural gas from the production wells drilled at different points from the injection well 301 will increases. As a result, the recovery of the oil contained in the underground oil reservoir 212 can be enhanced.

Further, when the structure has the dual channel pipe as in the present embodiment, since it can be handled as a single pipe, the effect of reducing a work over cost and a down hole tools cost is expected.

Although the embodiments of the present invention have been described above, the embodiments have been presented as examples, and the scope of the present invention is not limited to the embodiments. The above-described embodiment can be performed in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. The above-described embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide a method for enhanced recovery of oil contained in an underground oil reservoir by using micro-bubbles.

REFERENCE SIGNS LIST

-   -   101, 201, 301: Injection well     -   102: Injection water     -   103: Injection gas     -   104, 204, 304: Water passage (water injection pipe)     -   105, 205, 305: Gas passage (gas injection pipe)     -   202 a: Pipe that constitutes two passages with two pipes     -   202 b, 202 c: Pipe that constitutes two passages with dual         channel pipe     -   203: Packer     -   210: Micro-bubble generator     -   211: Ground surface     -   212: Underground oil reservoir 

1. An enhanced oil recovery method for enhanced recovery of oil contained in an underground oil reservoir by using an injection well including two passages of a gas passage and a water passage arranged inside the gas passage, the enhanced oil recovery method comprising: a step of injecting injection water from the water passage; a step of injecting an injection gas from the gas passage and spraying the injection gas as a fine gas bubble flow through a micro-bubble generator which is installed at a lower end of the gas passage; and a step of penetrate into the underground oil reservoir a gas-liquid mixture fluid containing micro-bubbles generated by mixing the injection water and the fine gas bubble flow in the injection well, wherein the micro-bubble generator is positioned at a depth of the underground oil reservoir, and the injection gas is injected between an inside of the gas passage and an outside of the water passage.
 2. The enhanced oil recovery method according to claim 1, wherein the water passage is a water injection pipe, and the gas passage is a gas injection pipe. 3.-5. (canceled) 